Comparative Changes in the Fatty-Acid Composition of Rat Cardiac Phospholipids after Long-Term Feeding of Sunflower Seed Oil- or Tuna Fish Oil-Supplemented Diets

Abstract

The fatty-acid composition of rat heart phospholipids was examined after long-term, i.e. more than 12 months, feeding of diets supplemented with n-6 fatty acids as sunflower seed oil (SSO), or n-3 fatty acids as tuna fish oil (TFO) which is a particularly rich source of docosahexenoic acid (DHA). Although some small changes occurred in the relative proportions of palmitic and stearic acids and in the ratio of total saturates to total unsaturates, the most important changes were in the relative proportions of 18:2 n-6 and 20:4 n-6 to 20:5 n-3 and 22:6 n-3. In general, the n-6/n-3 ratio of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and diphosphatidyl glycerol (DPG) was altered in favour of the family of fatty acids administered, although the proportions of the individual long-chain polyunsaturated fatty acids which contributed to this ratio varied from one class of phospholipids to another. In cardiac PC and PE, feeding TFO supplements reduced the proportions of arachidonic acid (AA) and significantly elevated (p < 0.01) the proportions of DHA but produced relatively little change in those of eicosapentenoic acid (EPA). In DPG, feeding TFO led to a significant increase in the proportion of AA as well as an increase in DHA. The level of EPA was relatively low in PC, PE and DPG even after TFO feeding and never reached comparable levels with that of either AA or DHA. Nevertheless the n-6/n-3 ratio in all these classes of major cardiac phospholipids was significantly reduced by feeding TFO compared to the SSO diet or the commercial rat chow (CC) reference group. In contrast to the reports of other workers who have studied the fatty-acid composition of platelet membranes after feeding various fish oil supplements, in the rat heart the major effect of tuna fish oil is an increase in the proportion of DHA rather than EPA in the cardiac phospholipids.

Artificial rearing with docosahexaenoic acid and n-6 docosapentaenoic acid alters rat tissue fatty acid composition

“…Dietary 22:6n-3 has been associated with decreased 20:4n-6 in various tissues (19)(20)(21)(22)(23)(24)(25)(26), and dietary 22:6n-3 is considered to compete directly with 20:4n-6. It has been suggested that feeding 22:5n-6 along with 22:6n-3 may maintain 20:4n-6 levels in tissues via 22:5n-6 retroconversion (19).…”

Changes in Phospholipid Fatty Acid Composition of Mouse Cardiac Organelles after Feeding Graded Amounts of Docosahexaenoate in Presence of High Levels of Linoleate

“…However, these changes in heart FA com position have been reported after feeding fish oil as such [12,27,28] or fish oils sup plemented by only low levels of LA, to avoid essential fatty acid (EFA) deficiency [11.26]. Therefore it is difficult to assess to what extent n-3 PUFA can modify cardiac mem brane FA composition in a balanced diet and subsequently affect membrane-bound en zyme activities, since n-3 and n-6 PUFA compete for incorporation into membrane tissues and further metabolism [1,4,9], In the present experiment, the magnitude of DHA incorporation into mouse cardiac membrane PL has been investigated by feed ing diets in which the supply of LA was maintained constant and the amount of DHA gradually increased.…”

“…The n-3 PUFA content of cellular phospholipids (PL) may also in fluence the activity of membrane associated enzymes and receptor functions [9,10]. The respective capacities of EPA and DHA in mediating these processes are poorly under stood, however, they do show significant dif ferences with respect to the magnitude [11,12] and specificity [ 13] of incorporation into tissue lipids, release from cell PL [14,15] and metabolism by cyclooxygenase [ 16] and lipoxygenase [17]. DHA is selectively incor porated in some tissues e.g.…”

“…13] and it appears to be enriched in 22 carbon PUFA [24], The manipulation of its FA composi tion by feeding sheep kidney fat [25] or fish oil to rats [11][12][13] or mice [26] leads to a greater increase of DHA PL content versus EPA. with a concomitant decrease of n-6 PUFA, which seems to influence cardiac basal functions [27] and decrease its suscep tibility to experimentally induced arrhyth mias [28].…”

Cytochrome P-450 Epoxygenase Metabolites of Docosahexaenoate Potently Dilate Coronary Arterioles by Activating Large-Conductance Calcium-Activated Potassium Channels

“…Thus, like prostaglandins, the epoxides present in tissues may reflect primarily which polyunsaturated fatty acids are available to act as substrate. Interestingly, dietary fish oils cause docosahexaenoate to preferentially accumulate in cardiac tissue (Charnock et al, 1986;Watkins et al, 2001) where polyunsaturated fatty acid cytochrome P-450 epoxygenases are known to reside (Fisslthaler et al, 1999;Tsao et al, 2001).…”